Apparatus and method for depositing a layer onto a substrate

ABSTRACT

Apparatus ( 1, 26 ) for depositing a layer ( 37, 38, 39 ) on a substrate ( 2 ) in a process gas comprises a chuck ( 3 ) comprising a first surface ( 4 ) for supporting the substrate ( 2 ), a clamp ( 4 ) for securing the substrate ( 2 ) to the first surface ( 14 ) of the chuck ( 3 ), an evacuatable enclosure ( 5 ) enclosing the chuck ( 3 ) and the clamp ( 4 ) and comprising an inlet, through which the processing gas is insertable into the enclosure ( 5 ), and control apparatus ( 19 ). The control apparatus ( 19 ) is adapted to move at least one of the chuck ( 3 ) and the clamp ( 4 ) relative to, and independently of, one another to adjust a spacing between the chuck ( 3 ) and the clamp ( 4 ) during a single deposition process while maintaining a flow of the processing gas and a pressure within the enclosure ( 5 ) that is less than atmospheric pressure.

The present invention relates to apparatus and methods for depositing alayer onto a substrate, in particular, a metallic layer onto a substratecomprising a semiconductor.

Layers may be deposited onto substrates using a variety of methods. Somemethods, for example electro-deposition, spray coating and dip coating,may be carried out at atmospheric pressure. Other deposition methods arecarried out at pressures lower than ambient atmospheric pressure bydepositing the layer within an evacuated enclosure. Deposition processesat reduced pressure may be referred to as vacuum deposition processes.Vacuum deposition processes include methods such as chemical vapourdeposition (CVD), including plasma enhanced chemical vapour deposition(PECVD) and physical vapour position deposition techniques, such assputtering and evaporation.

The various methods may be combined to produce a suitable layer. Forexample, a vacuum deposition treatment may be used to deposit a seedlayer on an insulating substrate and an atmospheric deposition method,such as electro-deposition, may be used to deposit a further layer ontothe seed layer.

WO 2011/061695 A2 discloses a method of processing a substrate thatdisplays outgassing when placed in a vacuum. The substrate may comprisea composite including semiconductor portions, for example in the form ofsilicon chips, embedded in a plastic matrix. One or more metallic layersare deposited onto this substrate to form a rewiring structure. WO2011/061695 A2 discloses a method by which outgassing from the substratemay be better controlled to achieve a steady state balance in which theoutgassing rate is determined solely by the diffusion rate in order toreduce the overall contamination of the substrate.

However, further improvements to apparatus and methods for depositinglayers on substrates, in particular metallic layers on substratescomprising semiconductive material are desirable.

A method for depositing a layer onto a substrate is provided thatcomprises the following. A substrate is inserted into an evacuatableenclosure and positioned between a clamp and a chuck arranged within theenclosure. Whilst a pressure within the enclosure is less thanatmospheric pressure, a processing gas is supplied to the enclosure, afirst layer is deposited onto the substrate whilst supplying theprocessing gas and whilst a first side of the substrate is spaced at adistance from the clamp. The clamp is brought into physical contact withthe first side of the substrate and a further layer is deposited ontothe first layer whilst maintaining the supply of the processing gas andthe pressure in the enclosure at less than atmospheric pressure andwhilst the clamp is in physical contact with the first side of thesubstrate and secures the substrate to the chuck.

According to this method, the layer is deposited on the substrate in atwo stage process. In the first stage, the first layer is depositeddirectly onto the surface of substrate whilst the clamp is spaced at adistance from the front side of substrate. In the second stage, theclamp is brought into physical contact with the first side of thesubstrate and, in particular, with the first layer already deposited onthe substrate. Both the stages are carried out in a single processsequence in which the pressure within the enclosure is maintained atless than atmospheric pressure and the supply of the processing gas tothe enclosure is maintained. The enclosure is, therefore, not opened tomove the clamp so that it is in physical contact with the substrate andsecures the substrate to the chuck. The two stage process including themovement of the clamp may be carried out automatically using a suitablyprogrammed control unit, for example.

The supply of processing gas is maintained and the pressure of theenclosure is maintained at less than ambient pressure during depositionof a layer when the clamp is not in contact with the substrate and whenthe clamp is in contact with the substrate. However, the phrasingmaintained is not used to limit the method to one in which the flow rateof the processing gas and the pressure is held constant, but includesmethods in which the flow rate of the processing gas supply and thelevel of the pressure may vary over the deposition time as long as thereis a supply of processing gas to the enclosure and the pressure withinthe enclosure remains at a value less than atmospheric pressure.

The method results in the deposition of a layer in which the regionspositioned under the clamp during the deposition of the further layerhave a thickness which is less than thickness of the total layer inregions not covered by the clamp during deposition of the further layer.The first layer may extend over the entire first side of substrate asthe clamp is spaced at a distance from substrates during the depositionof first layer. Therefore, the first layer can act to protect thematerial of the substrate from direct physical contact with the clamp.

In an embodiment, the substrate is placed in contact with a firstsurface of a chuck before depositing the first layer. The first layermay then be deposited whilst the substrate is supported on the firstsurface of the chuck. The substrate may also be in physical contactwith, and be supported on, the first surface of the chuck during thedeposition of the further layer. The clamp is also in physical contactwith the opposing side of the substrate during the deposition of thefurther layer so that the substrate can be considered as beingmechanically sandwiched between the clamp and the chuck duringdeposition of the further layer.

In an embodiment, the substrate is placed on moveable pins, for exampleextendable and retractable pins, which protrude above the first surfaceof the chuck and space the substrate at a distance from the chuck. Thesubstrate may be placed on the first surface of the chuck by retractingthe pins. The pins act as a loading/unloading system for the substrate.A loading arm for inserting the substrate into the enclosure may betteravoid coming into contact with the chuck by the use of these movablepins. Scratching of the rear side of the wafer is also better avoided asit does not slide mechanically across the surface of the chuck.

In an embodiment, the clamp is supported on movable pins and the pinsare moved so as to position the clamp spaced at a distance above thefirst side of the substrate during deposition of the first layer. Theclamp is movable with respect to the substrate and with respect to thechuck and independently of the position of the substrate and of thechuck. This not only enables deposition of a layer without the clampbeing in contact with the substrate and whilst the clamp is in contactwith the substrate, but also allows such a method to be carried out forsubstrates having different thicknesses. This embodiment also allows forthe target to substrate distance to be adjusted for a physical vapourdeposition process in which material from a source, commonly referred toas a target, is deposited onto the substrate.

The clamp may be brought into contact with the first side of thesubstrate by retracting the pins. This may be carried out after apre-determined time span and/or after the first layer has reached apre-determined thickness. The thickness of the first layer may becontrolled by pre-defining the deposition time, i.e. the time span.Alternatively, the thickness of the first layer may be monitoreddirectly and when it is determined that the first layer has the desiredthickness, the clamp may be brought into contact with the substrate byretracting the pins.

In some embodiments, the chuck is movable and the chuck is movedrelative to, and independent of, the clamp and the clamp is brought intocontact with the first side of the substrate. In these embodiments, theclamp may be immovable or movable.

In an embodiment, the first layer is deposited without active cooling ofthe substrate. This avoids the possibility that the substrate moves dueto the active cooling. This may occur if a gas flow is used to activelycool the substrate, for example.

The further layer may be deposited with active cooling of the substrate.The active cooling may be switched on after the substrate has beensecured to the substrate by the clamp. In this embodiment, movement ofthe substrate due to the active cooling is avoided, since the clampsecures the substrate to the chuck, thus preventing movement of thesubstrate during the deposition of the further layer.

The substrate may be actively cooled by passing a flow of gas over asecond side of the substrate or over the chuck. The chuck may comprise acooling circuit through which a liquid or a gas flows to remove heatfrom the chuck and, therefore, from the substrate detachedly attached tothe chuck.

The method may be used for physical vapour deposition methods andchemical vapour deposition methods. In the case of physical vapourdeposition of material from a material source, energy is applied to amaterial source comprising the material to be deposited whereby portionsof the material source are removed, deposited onto the substrate andform a layer on the first side of the substrate.

The material source may be a disc of solid material in the case ofsputter deposition or an irregular shape in the case of thermal orelectron beam evaporation. The energy to be supplied also depends on thetype of deposition. In the case of sputtering, it may be the applicationof a voltage to the material source. In the case of evaporation, it maybe directing an electron beam onto the source material, for example.

The portions of the material source that are removed may comprise one ormore metal elements which are deposited onto the substrate and form ametallic layer on the substrate. The metallic layer may be electricallyconductive.

If chemical vapour deposition techniques are used, the method furthercomprises supplying gaseous material to the enclosure. The gaseousmaterial may comprise one of more compounds with one or more elementswhich are to be deposited onto the substrate. The compounds decomposewithin the chamber, releasing the one or more elements which aredeposited onto the substrate and form a layer. The further componentsformed from the decomposition of the gaseous material, such as organicmolecules and/or oxygen, are removed from the enclosure by an evacuationand trap system.

The gaseous material may be selected so that the one or more elementsreact within the chamber and are deposited onto the substrate and form ametallic layer on the substrate.

In an embodiment, the substrate comprises a semiconductor, or asemiconductor wafer, or a composite comprising semiconductor portionsembedded in a plastic matrix. The layer deposited on these substratesmay be an electrically conductive metal layer. The metal layer mayprovide the rewiring layer for integrated circuit devices included inthe semiconductor, metallization or may serve as an electricallyconductive seed layer onto which a thicker metal layer is grown, forexample by electro- or galvanic deposition.

The first layer is deposited for a first time span and the further layeris deposited for a second time span. The first and second time spans maybe pre-defined in order that the first layer and the further layer havea pre-defined thickness. This method may be used if the deposition rateof the material forming the first and further layer is known.

In an embodiment, the first layer and the further layer are depositedover a total time span and the first time span is between 1% and 50% ofthe total time span or the first time span is between 10 to 20% of thetotal time span. The second time span is between 50% and 99% of thetotal time span or between 80% to 90% of the total time span.

A shorter time span for the first layer may be desirable if thesubstrate is not actively cooled during deposition of the first layer inorder to limit the temperature rise of the substrate.

A longer time span for the first layer may be desirable if the regionsunder the clamp during the deposition of the further layer are to have agreater thickness. For example, very thin metallic layers may have ahigh resistance which may be undesirable if the thinner regions of thelayer are to serve as electrically conductive contact areas for example.

Apparatus for depositing a layer on a substrate in a processing gas isalso provided. The apparatus comprises a chuck comprising a firstsurface for supporting a substrate, a clamp for securing the substrateto the first surface of the chuck, an evacuatable enclosure enclosingthe chuck and the clamp and having an inlet through which the processinggas is insertable into the enclosure, and control apparatus. The controlapparatus is adapted to move the chuck and/or the clamp relative to, andindependently of, one another to adjust the spacing between the chuckand the clamp during a single deposition process whilst maintaining aflow of the processing gas and a pressure within the enclosure that isless than atmospheric pressure.

The apparatus is suitable for reduced pressure deposition processingtechniques as the enclosure is evacuatable. The apparatus is alsosuitable for carrying out the method according to one of the previouslydescribed embodiments as the control apparatus is adapted to move thechuck and/or clamp relative to one another during a single depositionprocess. The enclosure does not have to be opened and the enclosure havean ambient atmosphere in order to move the chuck and/or clamp relativeto one another.

The control apparatus may be adapted to provide this feature by beingsuitably programmed to control actuating means which are coupled to theclamp and/or chuck. The actuating means are coupled to the clamp and/orchuck positioned within the enclosure such that the clamp and/or chuckmay be moved without breaking the vacuum or seal of the enclosure.

In an embodiment, the control apparatus is adapted to bring the clampinto physical contact with the substrate and secure the substrate to thefirst surface of the chuck during a single deposition process whilstmaintaining a flow of the processing gas and whilst maintaining apressure within the enclosure that is less than atmospheric pressure.

For example, the control apparatus may be adapted to move the clampand/or chuck such that a pre-defined distance which corresponds to thethickness of the substrate is provided between the clamp and the chuckthereby mechanically securing the substrate between the clamp and thechuck. Alternatively, the control apparatus may be adapted to withdrawsupport to the clamp to allow the clamp to rest under its own weight onthe substrate and mechanically secure the substrate to the chuck.

The apparatus may further comprise a first height adjuster forsupporting the clamp. The first height adjuster is moveable to adjustthe distance between the clamp and the chuck.

The apparatus may also further comprise a second height adjuster forsupporting the substrate, the second height adjuster being moveable toadjust the distance between the substrate and the chuck and to adjustthe distance between the substrate and the clamp.

A third height adjuster for adjusting the height of the chuck relativeto the clamp may also be provided.

At least one of the first height adjuster and the second height adjustermay comprise a plurality of pins, for example three pins. The pins aremoveable in directions perpendicular to the major plane of the clamp andthe first surface of the chuck.

In an embodiment, the clamp comprises an undercut in a surface facingtowards the first surface of the chuck. The undercut may be positionedso as to reduce the contact area between the clamp and the substratewhile, at the same time, the portion covering the cutout provides alarger shielding or masking effect due to the portion protruding overthe undercut.

The clamp may comprise a surface that faces towards the first surface ofthe chuck and is generally parallel to the first surface of the chuck.This surface provides a clamping surface for securing the substrate tothe first surface of the chuck. This arrangement is suitable forsecuring planar substrates such as wafers to the chuck.

The material to be deposited onto the substrate typically impinges thefirst side of the substrate from directions above the clamp since theclamp is positioned adjacent the first side of the substrate. In thiscase, the material to be deposited onto the substrate may also bedeposited on the clamp, for example in regions of the clamp immediatelyadjacent the substrate.

In an embodiment, the clamp comprises a roughened surface that facesaway from the first surface of the chuck. The material which isdeposited onto the substrate also tends to be deposited on the clamp atleast in regions immediately adjacent the substrate. The roughenedsurface increases the adhesion of the deposited material to the clampand prevents it from flaking or becoming detached whereby it may fallonto the substrate and contaminate the substrate.

The apparatus may further comprise cooling apparatus for cooling thechuck. The cooling apparatus may comprise a cooling circuit with a heatexchanger positioned outside of the enclosure. A coolant such as a gasor a liquid may be forced to flow through the cooling circuit so as toremove heat from the chuck and, consequently, from a substrate incontact with the chuck by thermal conduction.

To enable deposition of a layer under reduced pressure, the apparatusmay further comprise an evacuation system for evacuating the depositionchamber. The evacuation system may comprise one or more vacuum pumps,for example a rotary pump and a diffusion pump or a rotary pump and aturbopump.

The apparatus may further comprise a holder for holding a materialsource comprising material to be deposited onto the substrate. Thisembodiment is used if the layer is to be deposited using a physicalvapour deposition technique such as sputtering or evaporation. Thematerial source may be arranged so that it directly faces the front sideof the substrate onto which the layer is to be deposited. In thisarrangement, the clamp is positioned between the substrate and thematerial source.

The apparatus may further comprise an energy source for supplying energyto the material source and for removing portions of the material source.These removed portions of the material source are deposited onto thesubstrate to build up the first layer and the further layer.

If the layer is to be deposited using chemical vapour deposition, theapparatus may further comprising a gas supply system for supplyinggaseous material to the evacuatable enclosure, the gaseous materialcomprising one or more elements to be deposited onto the substrate inthe form of a layer.

In an embodiment, the control apparatus is programmed to move the clamprelative to the substrate after a pre-determined deposition time andsecure the substrate to the chuck with the clamp. This control apparatusenables the thickness of the first layer in the regions positioned underthe clamp to be defined by the pre-determined deposition time.

The apparatus may further comprise a layer thickness monitor. In thisembodiment, the control apparatus may be programmed to move the clamprelative to the substrate and secure the substrate to the chuck with theclamp after the first layer has a pre-defined thickness. A thicknessmonitor may be used if the thickness of the deposited layer cannot bepre-defined by the deposition time span or is not sufficientlyaccurately estimatable by measuring the deposition time.

Embodiments will now be described with reference to the drawings.

FIG. 1 illustrates apparatus according to a first embodiment fordepositing a layer on a substrate by sputtering,

FIG. 2 illustrates apparatus according to a second embodiment fordepositing a layer on a substrate by plasma enhanced chemical vapourdeposition,

FIG. 3 illustrates an arrangement for depositing a layer on a substrateusing only a shadow mask,

FIG. 4 illustrates an arrangement for depositing a layer on a substrateusing only a clamp,

FIG. 5 illustrates arcing during deposition of electrically conductivelayers on insulating substrates,

FIG. 6 illustrates a method for depositing a layer on a substrate duringwhich the clamp is moved with respect to the substrate,

FIG. 7 illustrates a clamp according to the present invention,

FIG. 8 illustrates movement of the clamp and the substrate relative to asource of material to be deposited.

FIG. 1 illustrates apparatus 1 for depositing a layer onto a substrate 2using sputter deposition. The apparatus 1 comprises a chuck 3 forsupporting the substrate 2, a clamp 4 for securing the substrate 2 tothe chuck 3 and an evacuatable enclosure 5, which encloses the chuck 3,the substrate 2, the clamp 4, and a target 6 comprising a source ofmaterial which is to be sputtered onto the substrate 2. In thisembodiment, the apparatus 1 comprises a magnetron sputtering arrangementand includes magnets 7 positioned behind a holder 8 onto which thetarget 6 is secured. The apparatus 1 includes a power source 9 applyinga voltage across the target 6.

Although the apparatus 1 is illustrated as having a single holder and asingle target, the apparatus is not limited to one holder and one targetand may include two or more holders each with a respective target.Similarly, two or more substrates each associated with a clamp may becoated with a layer at the same time.

The apparatus 1 also includes an evacuation system 10 for evacuating theenclosure 5 and reducing the pressure within the enclosure 5 to lessthan ambient atmospheric pressure. The apparatus 1 further includes agas supply system 11 for supplying processing gas into the enclosure 5and a backside cooling system 12 for actively cooling the chuck 3 and arear surface 13 of the substrate 2 when it is placed on a first surface14 of the chuck 3. The backside cooling system 12 may comprise a flow ofhelium gas.

The clamp 4 is positioned between the target 6 and the chuck 3 so thatthe clamp 4 is positioned above a first side 15 of the substrate 2. Theclamp 4 has the form of a ring having an inner diameter, which isslightly smaller than the outer diameter of the substrate 2 to enablethe clamp 4 to contact the peripheral region of the substrate 2 andsecure it in position on the chuck 3.

The clamp 4, the substrate 2 and the chuck 3 are each movable relativeto one another and independently of one another so as to adjust thedistance of the clamp 4 from the first side 15 of the substrate 2,indicated in FIG. 1, with reference number 16 and the distance betweenthe rear surface 13 of the substrate 2 and the first surface 14 of thechuck 3, as indicated by reference number 17 in FIG. 1.

In particular, the height of the first surface 14 of the chuck 3, thefirst side 15 of the substrate 2 and clamp 4 relative to base 18 of theenclosure 5 and relative to the target 6 is adjustable by means of aplurality of height adjusting means whose position is controlled bycontrol unit 19. The mechanical means for adjusting the height of thesubstrate 2, the chuck 3 and the clamp 4 may be positioned outside ofthe enclosure 5 to reduce the number of moving parts positioned withinthe enclosure 5 and simplify the construction of the apparatus 1.

The height of the clamp 4 and of the substrate 2 may be adjusted bymeans of height adjusters in the form of retractable pins, for example.Movement of the clamp 4 is illustrated in FIG. 1 with arrow 20, themovement of the substrate 2 is illustrated with arrow 21 and movement ofthe chuck 3 is illustrated by reference number 22.

The position of the substrate 2, the chuck 3 and the clamp 4 may beadjusted by the control unit 19 whilst the enclosure 5 contains apressure which is less than ambient atmospheric pressure and whilst theprocessing gas is supplied by the gas supply system 11 into theenclosure 5. The control unit 19 is positioned outside of the enclosure5. The connections between the control unit 19 and the height adjustersthrough a wall defining the enclosure 5 are vacuum tight so that theposition of the substrate 2, the chuck 3 and the clamp 4 may be changedwhilst the enclosure has a pressure which is less than atmosphericpressure.

In an embodiment, the position of the substrate 2, the chuck 3 and theclamp 4 may also be adjusted by the control unit 19 whilst the voltageis applied to the target 6 and material is deposited onto the substrate2. This enables the position of the clamp 4 relative to the substrate 2to be adjusted during the deposition of a film onto the first side 15 ofthe substrate 2.

The apparatus 1 may be used to deposit a layer onto the substrate 2using the following method.

In an embodiment, the substrate 2 is positioned on pins 23 whichprotrude through the chuck 3 spacing the rear surface 13 of substrate 2from the first surface 14 of the chuck 3 by a distance indicated withreference number 17. This position can be denoted as the load/unloadposition. The pins 23 are then retracted so that the rear surface 13 ofthe substrate 2 comes into contact with the first surface 14 of thechuck 3. A voltage is supplied to the target 6 and a first layercomprising elements of the target 6 is deposited onto the first side 15of substrate 2 whilst the clamp 4 is positioned above, and spaced at adistance from, the first side 15 of the substrate 2 as indicated in FIG.1 by distance 16.

After a predefined first time span and, therefore, after the depositedlayer has reached a predefined thickness, the pins 24 supporting theclamp 4 are retracted, lowering the clamp 4 in a direction towards firstside 15 of the substrate 2 until a lower inner surface 25 of the clamp 4is in physical contact with the first side 15 of substrate 2 and securesthe substrate 2 to the chuck 3. During this process, the reducedpressure of the enclosure 5 is maintained and a supply of processing gasinto the enclosure 5 is maintained. Additionally, the voltage, i.e.power, supplied to the target 6 is also maintained and a further layeris deposited on the first side 15 and, in particular, onto the firstlayer already deposited on the first side 15 of the substrate 2 whilstthe clamp 4 is in contact with the substrate 2 and secures the substrate2 to the chuck 3.

As is illustrated in more detail in FIG. 6c , the lower inner surface 25of the clamp 4 is in contact with edge regions of the first layerdeposited on the first side 15 of substrate 2 whilst the clamp 4 is incontact with the substrate 2. In this position, the clamp 4 preventsdeposition of material in the peripheral regions of the substrateresulting in a layer in which a central portion is thicker than aperipheral portion.

During a first time span, when the first layer is deposited without theclamp 4 being in contact with the first side 15 of the substrate 2, thechuck 3 is not actively cooled. This ensures that a flow of gasproviding the backside cooling system 12 does not affect the position ofthe substrate 2 on the first surface 14 of the chuck 3 as, during thisstage of the deposition process, the substrate 2 is supported only byits own weight on the first surface 14 of the chuck 3.

During a second stage of the deposition of the layer, after the clamp 4secures the substrate 2 to the first surface 14 of the chuck 3, thebackside cooling system 12 can be switched on as the clamp 4 secures thesubstrate 2 to the chuck 3. The further layer is deposited for a secondtime span during which the substrate 2 is actively cooled by thebackside cooling system 12.

The substrate 2 may be a semiconductor wafer such as a silicon waferwhich is typically generally circular and planar. The substrate 2 may bea composite substrate including a plurality of semiconductor devicesarranged in a regular array and embedded in a plastic matrix. Thesubstrate may also include an upper insulating layer such as a polyimidelayer. This upper insulating layer may be structured to exposeunderlying electrically conductive contact regions. The apparatus 1 maybe used to deposit a metal layer onto this substrate which issubsequently structured to provide a rewiring layer for thesemiconductor devices.

FIG. 2 illustrates apparatus 26 according to a second embodiment fordepositing a layer on a substrate 2. Apparatus 26 differs from theapparatus according to the first embodiment in that the layer isdeposited using plasma enhanced chemical vapour deposition rather thansputtering. Therefore, the apparatus 26 does not include a source ofmaterial positioned within the enclosure 5, but comprises a firstelectrode 27 positioned within the enclosure 5 opposing the chuck 3,which serves as a second electrode.

The gas supply system 11 of apparatus 26 is adapted to provide gascomprising compounds with one or more elements which are to be depositedon the first side 15 of substrate 2. This gas is fed into the enclosure5, which is held at a pressure less than the ambient atmosphericpressure, and decomposes within the volume 29 defined between the twoelectrodes 3, 27 and positioned above the first side 15 of substrate 2in which a plasma is formed so that the metallic element or elements aredeposited on the front side 15 of the substrate 2 and form a layer onthe first side 15 of the substrate 2.

The apparatus 26 includes a chuck 3, onto which the substrate 2 ispositioned, and a clamp 4 as in the first embodiment. As in the firstembodiment, the position of the chuck 3, the substrate 2 and the clamp 4are adjustable with respect to one another and independently of oneanother, in order that the substrate 2 may be brought into contact withthe first surface 14 of chuck 3 and the position of the clamp 4 relativeto the first side 15 of substrate 2 may be adjusted during deposition ofa layer onto the first side 15 of the substrate 2.

The apparatus 26 may be operated as in the first embodiment. Whilst theclamp 4 is spaced at a distance in front of the first side 15 substrate2 a first layer is deposited from the chemical vapour onto the firstside 15 of the substrate 2. Subsequently, whilst the enclosure 5 ismaintained under reduced pressure and the processing gas is supplied tothe enclosure 5, the clamp 4 is brought into physical contact with firstside 15 of substrate 2 comprising the first layer, such that the clamp 4secures the substrate 2 to the first surface 14 of the chuck 3 and thedeposition process continues to deposit a further layer in regions ofsubstrate 2 not contacted by the clamp 4.

As in the first embodiment, in the first stage in which the clamp 4 isspaced distance from the substrate 2, the chuck 3 is not activelycooled. After the clamp 4 is brought into physical contact with thesubstrate 2, the backside cooling is switched on to actively cool therear side 13 of the substrate 2 during the subsequent deposition of thelayer onto the opposing first surface 15 of the substrate 2.

This invention relates to a system or apparatus for processingsubstrates, such as semiconductor wafers, with an improved clampingdevice which may be used for combined PVD processing without and withwafer clamping or combined CVD processing without and with waferclamping in the same process chamber.

Further, a method for manufacturing a substrate like a wafer, inparticular, a semiconductor wafer, is provided wherein the substrate isbeing processed while being not clamped during a first time span andclamped during a second time span within the same processing sequence.The method is applicable for physical vapour deposition and othertreatment technologies under reduced pressure. A typical, but notlimiting application is seed layer deposition for later electroplating.In this application a thin conductive layer is deposited on a substrateincluding its surface structures and serves as seed layer for a latergalvanic deposition of metal, also described as electroplating orelectro-deposition.

Processing as defined herein includes any chemical, physical ormechanical effect acting on substrates.

Substrates as defined herein are components, parts or workpieces to betreated in a processing apparatus. Substrates include, but are notlimited to, flat, plate shaped parts having rectangular, square orcircular shape. In an embodiment, the substrates are essentially planar,circular substrates, such as semiconductor wafers or composite waferscomprising semiconductor chips embedded in a plastic matrix.

A vacuum processing or vacuum treatment system or apparatus comprises atleast an enclosure for substrates to be treated under pressures lowerthan ambient atmospheric pressure.

A chuck is a substrate holder adapted to fasten a substrate duringprocessing. This clamping may be achieved, inter alia, by electrostaticforces (electrostatic chuck ESC), mechanical means or both. Chucks mayexhibit additional facilities like temperature control components(cooling, heating) and sensors (substrate orientation, temperature,warping, etc.)

CVD or Chemical Vapour Deposition is a chemical process allowing for thedeposition of layers on heated substrates. One or more volatileprecursor material(s) are being fed to a process system where they reactand/or decompose on the substrate surface to produce the desireddeposit. Variants of CVD include:

Low-pressure CVD (LPCVD)—CVD processes at sub-atmospheric pressures;Ultrahigh vacuum CVD (UHVCVD)—CVD processes typically below 10⁻⁶ Pa/10⁻⁷Pa, and Plasma methods like Microwave plasma-assisted CVD (MPCVD),Plasma-Enhanced CVD (PECVD)=CVD processes that utilize plasma to enhancechemical reaction rates of the precursors.

Physical vapor deposition (PVD) is a general term used to describe anyof a variety of methods to deposit thin films by the condensation of avaporized form of a material onto a surface of a substrate (e.g. ontosemiconductor wafers). The coating method involves purely physicalprocesses such as high temperature vacuum evaporation or plasma sputterbombardment. Examples of PVD processes include Cathodic Arc Deposition,Electron beam physical vapor deposition, Evaporative deposition, Sputterdeposition (i.e. a glow plasma discharge usually confined in a magnetictunnel located on a surface of a target material).

The terms layer, coating, deposit and film are interchangeably used inthis disclosure for a film deposited in vacuum processing equipment, beit CVD, LPCVD, plasma enhanced CVD (PECVD) or PVD (physical vapourdeposition)

FIGS. 3 to 8 illustrate schematic views of one side of a symmetricalapparatus arrangement.

FIG. 3 illustrates a clampless system with a shadow mask 33 positionedspaced at a distance above the first surface 15 of the substrate 2 sothat it is positioned between the substrate and the source of materialto be deposited on the first surface 15 of the substrate 2. Thesubstrate 2 is arranged on a pedestal or chuck 3. Typically, a shadowmask 33 and a protection ring 34 are used for the protection of regionsaround the chuck 3, namely the chuck top, pins etc. The deposited film30 covers the whole exposed upper substrate surface 15 as is illustratedby arrows 35. This arrangement has the possible advantages that it iseasy, simple, cheap, reliable, no risk of wafer damage and completeupper surface is exposed to the deposition step. Therefore, it ispossible to later contact the wafer on the very outer edge forelectroplating. The possible disadvantage of this arrangement is that itis not possible to use backside gas to cool the wafer.

FIG. 4 illustrates a mechanical clamping system. A clamp 4 mechanicallyfixates substrate 2 to the chuck 3. A small edge area is used to holdthe substrate 2 and thus cannot be processed, i.e. material cannot bedeposited underneath the clamp 4 in peripheral regions of the substrate2. This is illustrated by retracted position of film 31 compared to theedge of the substrate 2. This arrangement has the possible advantagesthat it is easy, simple, cheap, reliable and allows backside gas andwafer cooling. However, it has the possible disadvantage that theuncoated substrate edge area provides no contact for electroplating andis therefore undesirable.

For the application of a seed layer for subsequent electroplating, eachof these methods may not be sufficient if applied individually. However,if a combination of the two systems were to be used to avoid the abovepossible disadvantages, two separate chambers would be required. Step 1:deposition of a seed layer in a first chamber having a “clampless”arrangement as illustrated in FIG. 3 followed by a clamped depositionprocess in a second chamber as illustrated in FIG. 4. The process wouldbe interrupted due to the need for two chambers.

Electrostatic clamping (ESC) could be used to secure the substrate tothe chuck. Electrostatic clamping allows backside gas and wafer coolingand full face deposition, but is expensive and not always reliable, forexample for dielectric substrates.

For wafer packaging processes such as seed layer deposition forelectroplating, typically, wafer cooling and full face deposition arerequired. At the same time for economic reasons these processes requiredto allow low costs at high reliability.

Furthermore especially in wafer packaging more and more differentsubstrate types are used, such as thinned silicon bonded on silicon,thinned silicon bonded on glass, polymer coated substrates and polymersubstrates with embedded dies. These different substrate types cannot behandled by a single type ESC; in some cases its application may be evenimpossible.

As an additional possible disadvantage of a pure mechanically clampedsolution is that in some cases, in particular when the deposition indeep features like TSV (through silicon via) is desired, the substratesmay be exposed to a comparably high ion current. This can, for example,in the case of poor dielectrics, lead to potential differences betweenthe clamp ring edge and the growing metal film. A spontaneous dischargebetween these different potentials can lead to damages of the growingmetal film, so called “arc trees” as is illustrated schematically inFIG. 5 by arrow 32.

These possible disadvantages can be avoided by use of the apparatusillustrated in FIGS. 1 and 2 as this apparatus may be used to use bothclampless and mechanically clamped arrangements within a singleenclosure and for a single process sequence without switching off theprocessing gas and without interrupting deposition of material onto thesubstrate 2.

The method of moving the clamp 4 relative to the substrate 2 and chuck 3during a single process sequence depositing a single film is illustratedin more detail in connection with FIG. 6.

FIG. 6a illustrates a substrate 2 loaded in the load position, where aclamp 4 having a ring-shape is resting on clamp lift pins 24, typicallythree pins 24, which are arranged adjacent to the substrate chuck 3 orprotection ring 34 respectively. In case of circular substrates, pins 24can be arranged with 120° angular distance. The second side 13 of thesubstrate 2 rests on wafer lift pins 23. The first side 15 of thesubstrate 2 comprises an insulating layer 36 in this embodiment.However, the insulating layer 36 is not mandatory and shall not limitthe scope of the invention.

The position of chuck 3 is adjusted as is illustrated in FIG. 6b suchthat the substrate lift pins 23 retract and the substrate 2 ispositioned on, and in physical contact with, the first surface 14 of thechuck 3. Chuck 3 is positioned until a first Target-substrate-distanceTSD 1 has been reached. This TSD 1 is close or equal to the selectedtarget substrate distance (TSD2) of the defined process.

FIG. 6b illustrates a so called shadow mask position, in which clamp 4rests on the clamp lift pins 24 at a distance x, which may be around 1to 5 mm, above the first side 15 of the substrate 2 This distance isselectable by adjustable clamp lift pins 24.

In the position illustrated in FIG. 6b , the process gas is switched onfirst to stabilize gas flow and pressure. No back side gas is used sincethe substrate 2 is not clamped. Backside cooling gas could otherwiseaffect the stable position of the substrate by lifting it.

Then the sputter power is switched on. If the process is using RF biason the chuck, it is preferably not switched on in the shadow maskposition as shown in FIG. 6b , since a first thin metal layer helpspreventing possible damage on devices on the wafer. Furthermore withoutRF bias, the thermal load on the substrate is lower in this step ofun-cooled operation. The sputtering time in shadow mask position is inthe range between 5 and 50%, preferably 10 to 20%, of the totalsputtering time depending on the requirements of electrical filmconductivity to the wafer edge and substrate cooling. For electroplatinga full face deposition of 10-50 nm is sufficient, depending on thematerial specific resistivity.

A first sub-layer 37 is deposited which covers the entire surface of thefirst side 15 of the substrate 2.

After having accomplished the shadow mask operation, the position of thechuck 3 is adjusted such that clamp 4 come into contact with thesubstrate 2 thus reducing the previous distance x to 0 as is illustratedin FIG. 6c . Clamp lift pins 24 retract from clamp 4 to a distance y.Thus the clamping force is given at least passively by the weight of theclamp 4 on the substrate 2. Of course also active means exerting activeholding forces to the substrate can be applied. This positioning stepcan be accomplished with or without switching off the sputter power.However, the process gas is not switched off.

In the clamp position illustrated in FIG. 6c , the weight of the clamp 4holds down the substrate 2 and secures it to the chuck 3 so that in thisprocess step back side gas can be applied. The temperature difference(delta T) introduced by the initial sputter step is already sufficientto establish is a heat flow from the substrate to the cold chuck, whichmay be kept at cryogenic temperature like −20° C. RF bias may be appliedif necessary.

A further sub-layer 38 is deposited in the first sub-layer 37 to fromlayer or film 39. The film thickness in this step depends on the timespan of the second deposition step and on the product to be processed.For example for a through silicon via (TSV) with a high aspect ratiolike in the range of 5:1 to 10:1 a film thickness between 1 and 2 μm maybe required to provide sufficient seeding in the via.

After the deposition is completed, the chuck 3 is moved directly in theload position for unloading as illustrated in FIG. 6 a.

The positioning steps as described above can be achieved by variousrelative movements of chuck 3, substrate 2 and clamp 4 in relation tothe target 6. Clamp 4 can be moved by means of lift pins 24, thesubstrate 2 by means of substrate lift pins 23 and/or the chuck 3 may bemoved relatively to the target. Depending on the construction of theprocess system various ways are possible to establish the relativemovement. In an embodiment of the invention, the process flow describedabove is assisted by software included in control unit 19. Establishingthe chuck height as a software parameter allows running automaticsequences of shadow and clamp mode position in production.

The adjustable clamp lift pin arrangement is used to select the shadowmask position or the clamp position. The distance x between clamp/shadowring 4 and substrate 2 may be selected depending on the inner diameterof the clamp ring and the nature of the sputtered material. For exampleCu or Au typically are more likely to scatter underneath edges thanother materials and low sticking coefficients for the clamp ring 4provide more material into gaps. This is different e.g. for Ti or Ta,where the deposition is typically more geometrically shadowed.

The layer 39 deposited onto the first side 15 of the substrate 2 has twosub-layers. A first sub-layer 37 extends to the edge of the substrate 2and a second sub-layer 38 is positioned on the first sub-layer 37. Thesecond sub-layer 38 has a lateral extent which is less than the firstsub-layer 37. The layer 39 has a greater thickness in its centre and thesmaller thickness at the periphery. This layer 39 can serve as anelectrically conductive seed layer for the subsequent electro-depositionof a further layer, i.e. a further layer will be grown on the seedlayer. The layer may comprise a metal or an alloy and may be describedas metallic.

FIG. 7 illustrates the form of the clamp 4 is more detail. The clamp 4typically has a ring-shape and typically uses an undercut 40 in itslower inner edge, i.e. in the region in which it contacts the substrate2. The absolute inner diameter of the clamp 4 may be 2 to 3 mm smallerthan the wafer radius, i.e. for a 300 mm wafer the diameter of the clampwould be in the range 294 to 296 mm, the actual contacting diameterbeing slightly higher due to the undercut of the clamp mask. In thatcase the shadow position of the disk above the wafer may be 2 to 4 mmabove the wafer surface for Ti sputtering, whereas the same distance is1 to 3 mm for Cu sputtering.

Typically the surfaces 41 directed towards the sputtering source or gapregions are either roughened, for example by sandblasting, or coatedwith layers, for example twin wire arc spray coating, preventingde-lamination of the growing film on the shields. As illustrated in FIG.7 also the surfaces 42 of the inner regions and gaps of the clamp ring 4needs to be prepared in such a way that a good adhesion of the scattereddeposition is provided as is indicated by the dashed line 43.

The protection ring 34 is a simply removable part of the shield set andis also prepared for a good adhesion of the deposited films as isindicated by the dashed line 43. The upper surface 44 of the protectionring 34 is lower than the chuck surface 14, so that the substrate 2 willnot touch the protection ring 34. However, the portion 25 of the clamp 4contacting the substrate 2 is cleaned carefully, e.g. mechanically withmild abrasives, to avoid sharp edges contacting and possibly damagingthe substrate 2.

FIG. 8 illustrates how the clamp 4 may be made adjustable for a wide TSDrange by adjustable pins 24. The clamp position of the clamp 4 isindicated with dashed line 45 and the clamp position is indicated bysolid line 46. This design includes a pump slot 47 between the clamp 4and a concentric cylindric shield 48 which provides an invariablepumping speed for a wide TSD range.

Some advantages arising are as follows:

full face deposition is possible with temperature control without theapplication of an ESC. A reduced film thickness to the wafer edge issufficient for a proper contact for electroplating;

a full face deposition step prior to clamped deposition avoids any riskof spontaneous discharges near the substrate edge, like arc trees, whichmay occur for some surface or substrate properties;

the possibility of running the two-step-process clampless/clamped in thesame chamber is provided;

a continuous process without interruption of the power is possible;

easy control of the process sequence by the chuck height as a softwareparameter is provided;

the method is adjustable for a wide range of TSD with shadow maskpositioning by pins with adjustable height, especially with a concentriccylindric shield setup providing invariable pumping speed, and

the method is applicable for different types of substrate such silicon,glass or polymer without any hardware change.

The invention claimed is:
 1. A method for depositing a layer onto asubstrate, comprising: inserting the substrate (2) into an evacuatableenclosure (5), and positioning the substrate (2) between a clamp (4) anda chuck (3) arranged within the enclosure (5), the chuck (3) including acooling circuit for circulating a liquid or a gas through the coolingcircuit, and whilst a pressure within the enclosure (5) is less thanatmospheric pressure: supplying a processing gas to the enclosure (5);depositing a first layer (37) onto a first side the substrate (2) whilstsupplying the processing gas and whilst the first side (15) of thesubstrate (2) is spaced at a distance from the clamp (4), bringing theclamp (4) into direct physical contact with at least a portion of thefirst layer (37) deposited on the first side (15) of the substrate (2),and depositing a further layer (38) onto the first layer (37) whilstmaintaining a supply of the processing gas, whilst maintaining thepressure in the enclosure (5) at less than atmospheric pressure andwhilst the clamp (4) is in physical contact with the at least a portionof the first layer and secures the substrate (2) to the chuck (3),wherein the clamp (4) does not contact the first side (15) of thesubstrate (2), wherein the first layer (37) is deposited without activecooling of the substrate (2) by not circulating the liquid or the gasthrough the cooling circuit, and wherein the further layer (38) isdeposited with active cooling of the substrate (2) by circulating theliquid or the gas through the cooling circuit.
 2. The method accordingto claim 1, further comprising placing the substrate (2) in contact witha first surface (13) of the chuck (3) before depositing the first layer.3. The method according to claim 1 or claim 2, further comprising:placing the substrate (2) on moveable pins (23) which protrude above thefirst surface (13) of the chuck (3) and space the substrate (2) at adistance from the chuck (3), and placing the substrate (2) on the firstsurface (15) of the chuck (3) by retracting the pins (23).
 4. The methodaccording to claim 1, further comprising: supporting the clamp (4) onmovable pins (24), moving the pins (24), and positioning the clamp (4)spaced at a distance above the first side (15) of the substrate (2)during deposition of the first layer (37).
 5. The method according toclaim 4, wherein the clamp (4) is brought into contact with the firstside (15) of the substrate (2) by retracting the pins (24).
 6. Themethod according to claim 1, wherein the chuck (3) is movable and thechuck (3) is moved relative to the clamp (4) and the clamp (4) isbrought into contact with the first side (15) of the substrate (2). 7.The method according to claim 1, further comprising applying energy to amaterial source (6) comprising material to be deposited whereby portionsof the material source (6) are removed, deposited onto the substrate (2)and form the layer (39) on the first side (15) of the substrate (2). 8.The method according to claim 7, wherein the portions of the materialsource (6) that are removed comprise one or more elements which aredeposited onto the substrate (2) and form a metallic layer on thesubstrate (2).
 9. The method according to claim 1, further comprisingsupplying gaseous material to the enclosure (5), the gaseous materialcomprising one or more compounds which react within the enclosure (5),releasing one or more elements which are deposited onto the substrate(2) and form the layer (39).
 10. The method according to claim 9,wherein the one or more elements deposited onto the substrate (2) form ametallic layer on the substrate (2).
 11. The method according to claim1, wherein the substrate (2) comprises a semiconductor.
 12. The methodaccording to claim 11, wherein the substrate (2) comprises asemiconductor wafer or a composite comprising semiconductor portionsembedded in a plastic matrix.
 13. The method according to claim 1,wherein a thickness of the first layer (37) is monitored duringdeposition and the clamp (4) is brought into contact with the at least aportion of the first layer when the first layer (37) has a pre-definedthickness.
 14. The method according to claim 1, wherein the first layer(37) is deposited for a first time span and the further layer (38) isdeposited for a second time span.
 15. The method according to claim 14,wherein the first layer (37) and the further layer (38) are depositedover a total time span and the first time span is between 1% and 50% ofthe total time span.
 16. The method according to claim 15, wherein thefirst time span is between 10 to 20% of the total time span.